1. Field of the Invention
The present invention relates to a piezoelectric vibrating piece, a piezoelectric vibrator, an oscillator, an electronic device, and a radio-controlled timepiece.
2. Description of the Related Art
In recent years, in mobile phones or personal digital assistants, a piezoelectric vibrator using a crystal or the like as a time source, a timing source of a control signal or a reference signal source, and the like has been used. Various piezoelectric vibrators of this kind have been provided, and a piezoelectric vibrator including a tuning fork type piezoelectric vibrating piece has been known as one example thereof.
The piezoelectric vibrator includes the tuning fork type piezoelectric vibrating piece described above, a plug, a case which hermetically seals the plug and the piezoelectric vibrating piece. The plug includes a pair of inner leads in which the piezoelectric vibrating piece is mounted, a plug main body which holds the inner leads. In addition, as shown in FIG. 15A, the piezoelectric vibrating piece 200 includes a pair of vibrating arm portions 211 which are disposed in parallel with a width direction, a base portion 212 which integrally fixes the base end portions of the pair of vibrating arm portions 211 in a length direction, a pair of excitation electrodes 213 which are formed on the vibrating arm portions 211 and vibrate the vibrating arm portions 211 when a predetermined driving voltage is applied, a mounting electrode 214 which is formed on the base portion 212 and is electrically connected to the pair of excitation electrodes 213 respectively, and a leading-out electrode 215 which connects the excitation electrodes 213 and the mounting electrode 214.
In addition, the pair of excitation electrodes 213, the mounting electrode 214, and the leading-out electrode 215 are an electrode layer 210 which is formed by laminating an underlying metal layer 210a (see FIGS. 16A and 16B) which is formed of chromium or the like, and a finishing metal layer 210b which is formed of gold or the like.
JP-A-9-326668 discloses a configuration in which the inner leads and the mounting electrode 214 are joined to each other through a joining member E′, such as solder, when mounting the piezoelectric vibrating piece 200 described above.
Generally, in order to strongly fix the piezoelectric vibrating piece 200 and the joining member E′, a material having high diffusibility with respect to the mounting electrode 214 (finishing metal layer 210b) is selected for the joining member E′. Accordingly, as shown in FIG. 15B, as time elapses, the joining member E′ diffuses on the electrode layer 210. This phenomenon significantly occurs when heat is applied to the joining member E′, such as in a case of hot-air mounting or the like.
As the diffused joining member E′ approaches the vibrating arm portions 211, an effect of a vibrating state (amount of deformation of the piezoelectric vibrating piece 200) becomes significant, and the frequency is shifted. Meanwhile, when a material having low diffusibility with respect to the mounting electrode 214 is used for the joining member E′, sufficient fixing strength is not obtained between the piezoelectric vibrating piece 200 and the joining member E′, and there is a concern that the piezoelectric vibrating piece 200 may separate from the joining member E′.
Thus, for example, as shown in FIG. 16A, a configuration is considered in which the finishing metal layer 210b in a portion (leading-out electrode 215 or excitation electrodes 213) other than the mounting electrode 214 from the electrode layer 210 of the piezoelectric vibrating piece 200 is removed to expose the underlying metal layer 210a. According to the configuration, as shown in FIG. 16B, since the diffusibility of the joining member E′ decreases in a portion other than the mounting electrode 214, it is possible to prevent diffusion of the joining member E′ to a portion other than the mounting electrode 214 while strongly fixing the piezoelectric vibrating piece 200 and the joining member E′.
However, in the configuration described above, it is necessary to pattern only the finishing metal layer 210b to expose the underlying metal layer 210a after collectively patterning the finishing metal layer 210b and the underlying metal layer 210a. Thus, it is problem in that the number of manufacturing processes and manufacturing costs increase.